(1) Field of the Invention
The present invention relates to a movable blade unit of wood cutting machine, and more particularly, to a movable blade unit which is smoothly movable along the rotating shaft with less friction.
(2) Description of the Prior Art
A conventional wood cutting machine includes an axle to which multiple blades are mounted so as to cut the wood object into multiple pieces. The distance between the blades can be adjusted. A movable blade unit is provided to meet different requirements of cutting and the blade on the movable blade unit can avoid from knots of the wood object or to cut along the terrain sides of the wood object to obtain the maximum use of the wood object.
The conventional wood cutting machine is shown in FIGS. 1 to 3, and generally includes an axle 10 and a rotating shaft 11 is connected to the axle 10, multiple blades 12 are mounted to the rotating shaft 11 by using a positioning ring 13 which is mounted to the rotating shaft 11. A hydraulic expansion mechanism in the rotating shaft 11 firmly positions the positioning ring 13 so that the blades 12 and the positioning ring 13 are co-rotated with the rotating shaft 11. Some machines may directly fix the blades 12 to the rotating shaft 11.
The rotating shaft 11 has at least one movable blade 16 which is connected to a movable ring 17. The at least one movable blade 16 and the movable ring 17 are located with another positioning ring 161 which is made from bronze copper and has multiple grooves so as to be engaged with transmission keys 15 on the rotating shaft 11. The positioning ring 161 is directly in contact with the rotating shaft 11 and movable axially along the rotating shaft 11 by moving the movable ring 17. The movable ring 17 has a flange 171 radially connected thereto and a bearing 172 is located between the flange 171 and the positioning ring 161. The users may move the flange 171 to move the movable ring 17. A bracket 173 is connected to the flange 171 and a measuring unit is used to detect the distance that the bracket 173 moves.
The at least one movable blade 16 is moved to a desired distance by operation of the flange 171 and the bracket 173 is then set at the desired position. The at least one movable blade 16 is then fixed and ready to cut.
The positioning ring 161 and the rotating shaft 11 has to be precisely matched to each other, while the positioning ring 161 has to be able to move smoothly on the rotating shaft 11. Therefore, the positioning ring 161 has to be made of bronze which is expensive. The contact friction between the positioning ring 161 and the rotating shaft 11 wears both and increases a gap between the positioning ring 161 and the rotating shaft 11. Dust and powder of the wood object can easily enter the enlarged gap to impede the movement of the movable ring 17.
There are several obvious drawbacks for the conventional movable ring 17. The gap between the positioning ring 161 and the rotating shaft 11, the machining precision for the bronze made positioning ring 161 is costly, and the wearing to the positioning ring 161 reduces the service of the positioning ring 161.
The present invention intends to provide a movable blade unit for wood cutting machines, wherein the drawbacks seen on the conventional movable ring are improved.